1. Field of the Invention
This invention relates to sandwich construction and, more particularly, to resinous foam sandwich construction in which the same resin is used to form the face sheets and the foam core, and the like.
2. Description of the Prior Art
"Sandwich construction", or panels formed from pairs of thin, parallel face sheets of relatively stiff material that are bonded to a common core have been used for a number of years. Aircraft flooring is a typical example of one of these many uses. There also is a need for a strong, low density material, for a combination of sandwich panel materials that will provide a wide range of controlled core densities, as well as for a material that will permit greater flexibility in choosing core and face sheet thicknesses.
Typically, the face sheets for these sandwich panels have been made of fiber reinforced material that is glued, or otherwise bonded, to a balsa wood or aluminum "honeycomb" core. Although these sandwich structures provide high strength-to-weight and stiffness-to-weight ratios, they are nevertheless subject to a number of disadvantages.
For example, one or more special steps must be taken during the manufacturing process to apply an adhesive to the core and face sheets and to press these treated materials together to establish an acceptable bond. There are, moreover, definite limitations with respect to the degree to which these sandwich panels can be re-shaped or formed after manufacture. In this connection, the possibility of re-shaping the blade of a sandwich construction hockey stick after manufacture to match individual needs is a clearly desirable feature. Prior art sandwich panels, however, do not have this post-forming capability. There also is a further limitation on the complexity of the sandwich panel shapes that can be manufactured because of the structural characteristics of the balsa and honeycomb core materials.
Thus, there is a need for sandwich panels that not only are more readily manufactured, resistant to laser beam penetration, and provide high strength-to-weight and stiffness-to-weight ratios, but which also can be produced in complicated shapes and provide some capability for post-forming.